Specifically some stuff from 1E:
• Exceptional strength percentile for fighters
• Ability limitations based on sex
• Class selection and level limitations based on race
...er... JUST KIDDING!...
Actually:
• Maximum PC HD. 1E-style HP parity between low-level vs. high-level. The 4-300+ range in 3e is simply ludicrous. A dagger/fire/falling should be at least some kind of threat throughout you're career.
• Titles for level. Maybe only for benchmark levels, to get an idea of rank/social standing/etc.
• Henchmen/Hirelings
• Keep/stronghold construction.
• Background profession. Each player gets one or two Professional skill(s) (farmer, limner, cabinetmaker, etc). Makes for some nice chrome, and removes the roleplayer vs. the min/maxer skill-selection issue.
• Duties, excises, fees, tariffs, taxes, tithes, and tolls.
• Conversion charts to Boot Hill and Gamma World... uh... sorry. Scratch that..
• The 1E proto-iconics from the bottom of the Random Dungeon Generation charts.
• Naked succubus